PS-6.4    Use the formula W = Fd to solve problems related to work done on an object.
Key Concepts:
Work   Force    Displacement   Joule
In solving work problems you must be able to Solve problems for any variables in the work equation and be able to determine the proper units required for the answer. Here are some examples.
Example #1. Finding work done when given the force and the displacement.  "How much work is done on a bicycle when it requires a force of 25N to move the bicycle a distance of 30m?"
The solution is:
      W= f  d
                W = 25N  x  30m
       W =
750J
***Remember that one Newton meter is equal to a Joule.
Here is another problem that is just a little different...
EXAMPLE #2.  200N of force is required to do 400J of work  to move a cart. How far was the cart moved?
In this example the work and the force are given in the problem. The original equation must be rearranged to solve for the distance.
Example #2:
 
Distance is equal to work divided by force. Our problem looks like this when it is set up.
D=W/f      D=400J / 200N    D=2m
Don't forget that a Joule is really a Newton meter, so Newton cancels out leaving the unit in the answer to be meters.
Here is another problem. In this problem we must rearrange the original work equation to solve for the applied force.
 
A forklift does 8000J of work lifting a crate to a height of 3m. What is the weight of the crate?
In this problem the weight of the crate is equal to the force applied to lift it. The work is done against gravity.
We will solve for the force.   F= W/D    F= 8000J / 3.0m   F= 2667N
Remember:
Force is given in newtons
Distance should be given in meters.
Work will be newton-meters or joules.
The displacement is always in the direction of the force.
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